I have one of the GearVendor units in my car and love it. I would have needed an Lentech or similar cost trans in order to handle the power of my stroker, I would have to replace the JetCoated headers with a set that would work with the AOD. Once I added up the costs of the AOD, headers, and all of the other parts required, the GV was less money. Mine at the time was $2495, I chose to have another driveshaft made to the correct length rather than shorten the original. I had modify the trans tunnel so the unit would clear the floor, the depression in the floor just after the shifter was pounded up a little, other than that no other mods.
I mounted the activation switch up and to the right of the dimmer switch, once on the highway, I just tap this switch and the over drive kicks in. Cruising at 70 or so, I'm turning about 2200 rpms, not bad with a 3.55 rear. There is a photo of the unit prior to the install sitting on my workbench somewhere in my CarDomain pages. It has never given me any trouble at all, and I installed it in my garage without a lift by myself.